Years Late, a High-Tech 'NextGen' Project to Unsnarl U.S. Aviation Is Beginning to Speed Flights

SEATTLE—America's new system to cut airline delays, itself years late, is finally yielding results. But halting progress, budget overruns and fights between regulators and airlines show how hard it will be to modernize the world's most complex air-traffic management network.

For Alaska Air Group Inc., the future has arrived. Since spring, pilots landing at its Seattle-Tacoma International Airport hub no longer descend in steps that...